TY - JOUR
T1 - Hydrolysis of α- and β-d-glucosyl fluoride by individual glucosidases
T2 - new evidence for separately controlled "plastic" and "conserved" phases in glycosylase catalysis
AU - Matsui, Hirokazu
AU - Tanaka, Yoshimasa
AU - Brewer, Curtis F.
AU - Blanchard, John S.
AU - Hehre, Edward J.
N1 - Funding Information:
* Supported by Research Grants DMB 89-04332 (to E.J.H.) from the National Science Foundation and CA-16054 (to C.F.B.) from the National Institutes of Health. ’ Research Associate in Microbiology and Immunology, on leave from the Department of Agricul-tural Chemistry, Hokkaido University, Sapporo, Japan. ’ Visiting Scholar in Microbiology and Immunology, on leave from the doctoral studies program, Department of Agricultural Chemistry, Hokkaido University, Sapporo, Japan. 3 Affiliated with the Department of Molecular Pharmacology. 4 Affiliated with the Department of Biochemistry. ** Corresponding author at: Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, N.Y. 10461, USA.
PY - 1993/12/16
Y1 - 1993/12/16
N2 - α-Glucosidases from sugar beet seed and ungerminated rice catalyzed the hydrolysis of β-d-glucopyranosyl fluoride to form α-d-glucose. The reactions were slow, with V/K = 11-15 × 10-3 or ∼ 1-2% of that for hydrolysis of p-nitrophenyl α-d-glucopyranoside, but were not due to any impurity in the substrate or to contaminating β-glucosidase or glucoamylase. Furthermore, almond β-glucosidase promoted hydrolysis of α-d-glucosyl fluoride to form β-d-glucose at an exceedingly low rate, V/K = 4 × 10-4. This weak reaction did not stem from any impurity in the substrate or to contamination with α-glucosidase or glucoamylase, but it was partly (∼ 20%) attributable to a trace of accompanying trehalase. That all three glucosidases acted upon both α- and β-d-glucosyl fluoride, albeit at low efficiency with the disfavored anomer, reflects the previously demonstrated ability of each enzyme's catalytic groups to respond flexibly to substrates of different types. That the disfavored d-glucosyl fluoride in each case was converted into a product of the same configuration as from enitols or favored d-glucosyl substrates provides additional evidence for the two-step nature of the chemical mechanisms of glucosidases, in which the stereochemistry of water attack on the enzyme-stabilized oxocarbonium ion is strictly maintained, regardless of the initial anomeric configuration of the substrate.
AB - α-Glucosidases from sugar beet seed and ungerminated rice catalyzed the hydrolysis of β-d-glucopyranosyl fluoride to form α-d-glucose. The reactions were slow, with V/K = 11-15 × 10-3 or ∼ 1-2% of that for hydrolysis of p-nitrophenyl α-d-glucopyranoside, but were not due to any impurity in the substrate or to contaminating β-glucosidase or glucoamylase. Furthermore, almond β-glucosidase promoted hydrolysis of α-d-glucosyl fluoride to form β-d-glucose at an exceedingly low rate, V/K = 4 × 10-4. This weak reaction did not stem from any impurity in the substrate or to contamination with α-glucosidase or glucoamylase, but it was partly (∼ 20%) attributable to a trace of accompanying trehalase. That all three glucosidases acted upon both α- and β-d-glucosyl fluoride, albeit at low efficiency with the disfavored anomer, reflects the previously demonstrated ability of each enzyme's catalytic groups to respond flexibly to substrates of different types. That the disfavored d-glucosyl fluoride in each case was converted into a product of the same configuration as from enitols or favored d-glucosyl substrates provides additional evidence for the two-step nature of the chemical mechanisms of glucosidases, in which the stereochemistry of water attack on the enzyme-stabilized oxocarbonium ion is strictly maintained, regardless of the initial anomeric configuration of the substrate.
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U2 - 10.1016/0008-6215(93)84153-W
DO - 10.1016/0008-6215(93)84153-W
M3 - Article
AN - SCOPUS:0027759648
SN - 0008-6215
VL - 250
SP - 45
EP - 56
JO - Carbohydrate Research
JF - Carbohydrate Research
IS - 1
ER -